1. Field of the Invention
The present invention relates to a method of signal processing including correlation analysis, and to magnetic character recognition methods.
2. Background Art
Banks, credit unions and other financial institutions regularly process checks, deposit slips, and other types of bank documents in order to execute financial transactions efficiently. Document processing systems have therefore become quite prevalent in the industry. Typically, information will be printed on these documents in magnetic ink which can be read both by the human eye and a computer. This form of printing is read by a process called magnetic ink character recognition (MICR). As part of the recognition process, a MICR magnetic read head is used to read the information printed on the document. Since the late 1950s when MICR was first introduced in banking, MICR reading was mostly performed in high-speed reader/sorters located in the central processing centers of financial institutions. Paper documents, namely checks, were deposited by account holders and initially processed by the depositing bank by performing a “proofing” operation where the debits would be equal to the credits, i.e., the deposit ticket including cash in and cash out slips. All checks that were drawn on other banks were high speed sorted by MICR reading only the amount field and routing fields, assembling items drawn on a single bank into bundles with a cash letter wrapping, and then physically transporting them to other banks by auto or airplane depending upon whether the other banks were local or distant. In many cases items drawn on all distant banks were grouped into a single large bundle and sent to the local Federal Reserve Bank for further processing and final distribution for presentment to the paying bank. Typically, documents read by these subsequent institutions have a MICR “can't read” rate lower than 2% after they have been high speed processed by the bank of first deposit. Documents with “rejects” in the MICR line are repaired with a bottom strip which is re-encoded with the MICR information or inserted into a carrier envelope where the MICR line data is also re-encoded in the proper location on the envelope.
Conventional approaches to MICR reading and recognition generally involve determining peak position information for a waveform generated by a single gap magnetic read head. This peak information typically includes information regarding the amount of time between the peaks of each character. Knowledge of the velocity of the document (and thus, the velocity of the characters which are printed on the document) allows this time information to be converted into distance information, which can be compared to each MICR character and the MICR character peak profiles as contained in the ANS X9.27-2000 “Print and Test Specifications For Magnetic Ink Printing (MICR)” as promulgated by the American National Standards Institute. Based on the design of the standard E-13B character set, in order that a MICR reader reliably read with a high correct character read rate and with a very low substitution rate, the document velocity must be precisely known during reading or otherwise be speed-controlled so that it does not vary.
In fact, typical designs for reliable MICR reading generally involve rather complex schemes for controlling the velocity of the document or attempting to measure its velocity at different times as the document moves past the MICR read head. It is easy to understand that these schemes have a tendency to increase design, processing, and manufacturing costs.
One such scheme is shown in U.S. Pat. No. 5,134,663, which describes a center-line magnetic ink character recognition system. By establishing a center line between the first and last peaks of a character, and working from the center line, errors due to speed are not accumulated at the end of the character with respect to the beginning scan read of the character. Similarly, U.S. Pat. No. 4,143,355 describes a character recognition system. This system generates clock pulses for use in detecting and decoding characters printed on a document derived from a mechanical clock pulse encoder moving in synchronism with the relative movement by the reading head of the system. The system shown in U.S. Pat. No. 5,091,961 describes a magnetic ink character decoder. A bank check reader operates without the necessity of a constant rate of check movement by imposing a set of flux reversals over the magnetic ink characters to be read. The flux reversals permit a pulse count sequence to be generated that is unique to each magnetic ink character independent of the rate of check movement. Although these approaches address problems associated with document velocity, there is still a need for an improved low-cost method of MICR character reading without the need for controlling the velocity of the document.
In order to reduce the costs of processing check payments and speed up the processing of check based payments to reduce fraud, the banking industry is developing various means of truncating the paper check at either the Point of Sale, the merchant depositor or within the bank of first deposit. In these cases, it is extremely important that the MICR read rate approach 100% with a substitution rate near zero percent because the original document may no longer be available to allow error correction when an error is detected later in the processing stream. While it has been cost effective to provide sophisticated methods with redundancy in centralized high-speed reader/sorters to improve upon the MICR read rate and reduce substitutions, the challenge is to provide improved MICR read performance in low cost systems that are positioned at the Point-of-Sale or at the teller window.
One such system may be seen in U.S. Pat. No. 4,087,789, which shows a complex recognition system for high speed MICR recognition that uses a matrix read system. Each character to be recognized is divided into a number of discrete vertical segments, each segment being individually magnetized by an ac-write head. The velocity at which the document is transported is sensed and time-correlated to the magnetization of each discrete segment to avoid irregularly spaced magnetization due to non-uniformities in transport velocity. However, the single gap magnetic read head is used for typical low speed MICR readers because those markets require a low cost MICR reader for applications such as at a teller window or at a Point-of-Sale.
In addition to problems associated with document velocity, electromagnetic noise is also a problem. In the environment of reading MICR from a check at a Point-of-Sale terminal there is considerable magnetic noise produced by the checkout conveyor system, receipt printer, the cash register, and the motor within the MICR reader itself. Several solutions have been proposed. One proposed solution is set forth in U.S. Pat. No. 5,887,075, which describes a method, apparatus, and article of manufacture for filtering periodic noise from a magnetic read head. Specifically, samples known not to contain a desired signal are used to extract a waveform representative of a single period of periodic noise. The representative waveform is synchronized with samples containing the desired signal and used to compensate the samples containing the desired signal in order to minimize, reduce, cancel or remove the effects of the periodic noise. U.S. Pat. No. 5,959,279 describes a magnetic pattern recognition method and apparatus capable of preventing magnetic noise from the stepper motor from affecting MICR character recognition processing while the stepper motor transports a document containing MICR characters. Many cycles of stepper motor noise signals are obtained to determine an average of the noise signals, which are then subtracted synchronously from the raw detection signals, to obtain the MICR character recognition data. Further, some known signal processing techniques that address noise are described in Signal Processing Using Analog And Digital Techniques, K. G. Beauchamp (New York: John Wiley & Sons, 1973), pp. 400–467. Although these approaches address noise reduction, as stated above, there is still a need for a low-cost solution of MICR character reading, which is suitable for low signal MICR documents in an environment that includes substantial magnetically or electrically induced noise that provides distortion in the MICR waveforms.